1. Field of the Invention
This invention relates to Field Emission Displays (FED,s) and the methods for fabricating FED's and more specifically to methods for attaching a face plate to the substrate of a FED.
2. Description of the Relevant Art
The problem addressed by this invention is encountered in the manufacturing of Field Emission Displays (FED's). FED's operate on the principle of cathodoluminescent phosphors excited by cold cathode field emission electrons as shown from a sectional view in FIG. 1 and a perspective view in FIG. 2. A face plate 2 or anode having a cathodoluminescent phosphor coating similar to that of a cathode ray tube receives patterned electron bombardment which can be seen by a viewer. The face plate 2 is separated from the base plate (substrate 6) or cathode by a vacuum gap of 10.sup.-9 Torr to 10.sup.-6 Torr and outside atmospheric pressure is prevented from collapsing the two plates together either by the tensile strength of each of the two plates or by spacers which are not shown in this figure. Arrays of electron emission sites (emitters 7) are typically cone shaped that produce electron emission in the presence of an intense electric field.
In the case of FIG. 1, and most field emission displays, a grid voltage is applied to the gates to control the flow of electrons from a particular set of emitters. There is a field of several hundred volts even up to one thousand between the cold cathode emitters and anode. The emission process is thoroughly discussed in the literature, and one useful explanation of it as directly applied to vacuum microelectronics can be found in Spindt et al., "Physical Properties of Thin Film Field Emission Cathodes with Molybdenum Cones," 47 J. APPLIED PHYSICS 5248 (1976), which is hereby incorporated by reference.
The substrate of a FED includes arrays of emission sites, and connections for addressing and activating the generation of electron beams from those sites. Many techniques are available for creating the emissions from arrays, addressing the emissions arrays, and activating the emissions sites. These techniques are discussed in the Spindt et al. paper above and in many U.S. patents, such as U.S. Pat Nos. 5,302,207 and 5,329,207, and are hereby incorporated by reference.
It is known that FEDs might be used to display images similar to the images displayed on CRT's. It is also known that to display an image using an FED that the volume inside the FED has to be evacuated to permit emitted electrons to freely travel through the volume surrounding the FED and impinge upon the face plate. Therefore, the enclosure for the FED should permit the FED to be sealed in an evacuated volume at a high vacuum level.
Therefore, it is a primary object of the invention to provide a method for attaching a face plate to a substrate of a field emission display while increasing the high vacuum between the anode and the Cathode.
It is another object of the invention to provide a method for fabricating a field emission display which has an increased vacuum compared the vacuum chamber where it is assembled.
It is yet another object of the invention to describe a method for improving the fabrication method of field emission displays.
This and other objects, features, and advantages of the invention will be apparent to those skilled in the art from the following detailed description of the invention, when read with the drawings and appended claims.